The present invention relates to an X-ray inspection device, for example, an X-ray inspection device and an X-ray inspection method that inspect the bonding condition of a component mounted on a printed circuit board, the bonding condition of the inside of a component packaged with resin or metal and the bonding condition of a component packaged within a printed circuit board.
In these years, devices such as PDA [personal digital assistant] have been miniaturized and upgraded, and in packaging electronic components in the devices, to package as many electronic components as possible in small space, increase in packaging density, face-down bonding of bonding an electrode provided on a lower face of the electronic components to a land of a printed circuit board, and built-in of electronic components of packaging the electronic components within a printed circuit board have been promoted.
Since a bonded part by the above-mentioned face-down bonding or a bonded part in the case of the packaging within a printed circuit board cannot be viewed directly, an inspection method of exposing a cross section of the bonded part and viewing the exposed cross section and a nondestructive X-ray inspection method of viewing the internal condition of an object to be inspected are used. When using the X-ray inspection method, it is possible to view the bonding condition of the inside of the object to be inspected. However, in the case that a plurality of components are packaged with being overlapped with each other, the components overlap each other in an X-ray image and therefore it is difficult to view the condition of each component accurately. For this reason, in conventional X-ray inspection devices, the object to be inspected is imaged at a plurality of positions by varying a direction of X-ray irradiation and an irradiation angle with respect to the object to be inspected, and a cross-sectional part to be viewed is taken from the X-ray image according to tomography or laminography and then viewed and inspected.
The conventional X-ray inspection device will be described below with reference to the appended drawings. The elements common to each conventional example are described by assigning the same reference numerals.
FIG. 18 is a block diagram showing the schematic configuration of a conventional X-ray inspection device by using tomography. The conventional X-ray inspection device shown in FIG. 18 is disclosed in, for example, the Official Gazette of Japanese Unexamined Patent Publication No. Hei 11-344453.
As shown in FIG. 18, an X-ray is irradiated from an X-ray irradiation device 103 into an object to be inspected 102 such as a printed circuit board held by a rotation device 101 and the X-ray that passes through the object to be inspected 102 is detected by an X-ray detection device 100. The X-ray irradiation device 103 is located on a direct extension of the rotation center of the rotation device 101 and an imaging center of the X-ray detection device 100 and emits the X-ray toward the X-ray detection device 100. A control device 104 controls the rotation position of the rotation device 101 and controls driving of the X-ray detection device 100 and the X-ray irradiation device 103. The control device 104 controls so that the X-ray irradiation device 103 radiates an X-ray when the rotation device 101 that holds the object to be inspected 102 is rotated at a predetermined rotation angle and the X-ray image passed through the object to be inspected 102 is captured in the X-ray detection device 100. At this time, the control device 104 is configured so as to allow the rotation device 101 to rotate one or a half revolution and the X-ray detection device 100 to take an image, and prepare an X-ray image of the cross-sectional part image to be viewed and display it.
As mentioned above, the conventional X-ray inspection device shown in FIG. 18 is configured so as to rotate the object to be inspected 102 around an axis orthogonal to an X-ray irradiation axis as a rotation axis. In the configuration of the conventional X-ray inspection device shown in FIG. 18, a distance A between an X-ray focus (spot position) of an X-ray source that the X-ray irradiation device 103 emits the X-ray and the rotation axis of the object to be inspected 102 and a distance B between the position of this rotation axis and a detection part of the X-ray detection device 100 are constrained by an outside dimension of the object to be inspected 102. This constraint means that a minimum value of the distance A must meet a condition of A>C/2 so that the outside dimension (dimension indicated by C in FIG. 18) of a printed circuit board as the object to be inspected 102 can rotate. Due to the constraint, the object to be inspected 102 cannot get closer to the X-ray irradiation device 103 so much. In the conventional X-ray inspection device shown in FIG. 18, in the case when the distance A+B that defines an arrangement space of object to be inspected is reduced, a value of A in (A+B)/A as a magnifying factor of the X-ray image is limited and therefore the magnifying factor cannot be increased. For this reason, the conventional X-ray inspection device shown in FIG. 18 has a problem that it is difficult to view a detailed condition of each component.
FIG. 19 is a block diagram showing a schematic configuration of a conventional X-ray inspection device by using laminography. The conventional X-ray inspection device shown in FIG. 19 is disclosed in, for example, the specification of U.S. Pat. No. 4,926,452.
In FIG. 19, a rotational X-ray irradiation device 105 has a function of controlling a thermal electron by rotating magnetic field and rotating and irradiating the X-ray at a predetermined position. An X-ray detection device 109 converts the X-ray that passes through the object to be inspected 102 such as a printed circuit board into a visible light in a scintillator 107 and then detects the light through a rotational mirror mechanism 108. A control part 106 controls driving of the rotational mirror mechanism 108 in synchronization with the rotating magnetic field of the rotational X-ray irradiation device 105. Further, the control part 106 controls the rotational X-ray irradiation device 105 and the X-ray detection device 109 for imaging and the X-ray inspection device obtains the tomographic image of the object to be inspected 102 at high speed and carries out inspection.
In the conventional X-ray inspection device shown in FIG. 19, an irradiation angle β with respect to the object to be inspected 102 is a fixed value physically determined in advance. Accordingly, when the object to be inspected 102 is moved closer to the rotational X-ray irradiation device 105, the object to be inspected 102 falls outside of the X-ray irradiation range, for example, at a position indicated by W in FIG. 19. For this reason, there causes a problem that even when the user ties to magnify the X-ray image by moving the object to be inspected 102 closer to the rotational X-ray irradiation device 105, the magnifying factor is constrained. Further, the conventional X-ray inspection device shown in FIG. 19 is complicated in configuration and expensive.
In another conventional X-ray inspection device, by slanting and rotating the X-ray irradiation device, and separating bonded parts overlapped with each other within the object to be inspected, the bonding condition of each bonded part is inspected. Such conventional X-ray inspection device is disclosed in, for example, the Official Gazette of Unexamined Patent Publication No. 2002-189002.
FIG. 20 is a view showing the schematic configuration of the conventional X-ray inspection device for inspecting the bonding condition by slanting and rotating the X-ray irradiation device.
The X-ray inspection device shown in FIG. 20 is configured so that an X-ray irradiation device 110 irradiates a printed circuit board and so on as the object to be inspected 102 with an X-ray obliquely. The X-ray radiated from the X-ray irradiation device 110 is configured so as to pass through the object to be inspected 102 and to be received in an X-ray detection device 115. The oblique radiography conducted in the conventional X-ray inspection device is performed by slanting the X-ray irradiation device 110. In this manner, the X-ray detection device 115 takes X-ray radioscopic images of the object to be inspected 102 by irradiating the object to be inspected 102 with the X-ray from various angles. As a result, based on these X-ray radioscopic images, it becomes possible to inspect the condition of the component at a desired position in the object to be inspected 102.
FIG. 21 is a block diagram showing a main part of the conventional X-ray inspection device shown in FIG. 20. In FIG. 21, the object to be inspected 102 is a circuit forming body consisting of a ball grid array 111 (hereinafter referred to as BGA) with a face-down bonded part, a printed circuit board 112 and an electronic component 113. The X-ray irradiation device 110 is slanted with respect to the object to be inspected 102 and the object to be inspected 102 is imaged in the X-ray detection device 115. FIG. 21 shows a scintillator 114 of the X-ray detection device 115.
A radiographic image indicated by F in FIG. 21 is an example of X-ray images at the time when the X-ray irradiation device 110 is located just below the object to be inspected 102 and the X-ray radiated from the X-ray irradiation device 110 shows the state in which components are overlapped with each other in the circuit forming body as the object to be inspected 102. A radiographic image indicated by G in FIG. 21 is an example of X-ray images detected by the X-ray detection device 115 when the X-ray irradiation device 110 is disposed obliquely and irradiates the object to be inspected 102 with the X-ray. Since the electronic component and the bonded part and the like exist in the circuit forming body as the object to be inspected 102 at different positions, the radiographic image F and the radiographic image G are different from each other due to difference in radiographic angle.
As shown in FIG. 21, although all of the bonded parts of BGA 111 cannot be inspected according to only the radiographic image F since the BGA 111 is blocked by the electronic component, the bonding condition of all bonded parts of the BGA 111 can be inspected by using the radiographic image G taken with the X-ray irradiation device 110 being slanted. That is, the position of the electronic component 113 is excluded from the inspected range and the bonded part of BGA is inspected, so that the condition of all bonded parts of the BGA can be inspected in a plurality of the radiographic images.
However, when packaging interval between the electronic components becomes narrower, influence of the electronic components on the different level from the cross section of the object to be inspected cannot be removed at any angle, thereby causing the problem that accurate information on the cross section of the object to be inspected cannot be obtained.